Summary

Heart rate variability (HRV)—the variation between successive heartbeats—reflects autonomic nervous system regulation and may provide useful information about cardiovascular health.

Reduced HRV generally indicates impaired vagal activity and autonomic dysfunction. It is associated with coronary artery disease, myocardial infarction, heart failure, arrhythmias, inflammation, metabolic dysfunction, stress and depression.
HRV may help with early detection and risk stratification, and lower values have been linked to higher risks of mortality, recurrent cardiac events, ventricular arrhythmias and sudden cardiac death. However, its predictive value often decreases after accounting for established measures such as ejection fraction and clinical risk scores.
HRV can be measured using time-domain, frequency-domain and nonlinear methods. Results depend heavily on recording duration, ECG quality, artefact correction, medications, age, sex and comorbidities.
Potential therapeutic applications include exercise, Mediterranean-style diet, smoking cessation, paced breathing/HRV biofeedback, pharmacological treatment, vagus-nerve stimulation and rehabilitation. These approaches may improve HRV, but it is not yet clear whether HRV changes directly cause better clinical outcomes.
Wearables and artificial intelligence could enable continuous monitoring and personalised treatment, particularly by detecting deteriorating HRV before heart-failure decompensation. Their accuracy and clinical usefulness still require validation.
Major barriers include inconsistent measurement protocols, limited long-term evidence, device reliability, uncertain additional predictive value, privacy concerns and the risk of overinterpreting HRV.

Overall conclusion

HRV is a promising, non-invasive adjunctive biomarker for cardiovascular assessment and personalised care, but it should not currently replace established diagnostic or prognostic tools. Wider clinical adoption requires standardised recording and analysis methods, larger prospective trials, and proof that HRV-guided treatment improves patient outcomes.